CHEMISTRY COMMUNITY

Diviya Khullar 1G

Yes because work is equal to pressure x $\Delta$ V and in a bomb calorimeter, pressure and volume are constant so w=0.

Diviya Khullar 1G

Yes, voltaic/galvanic cells will have a salt bridge or porous disk for ion transfer to prevent charge build-up.

Diviya Khullar 1G

The salt bridge transfers ions to prevent charge build-up and allow e^- transfer.

Diviya Khullar 1G

There are different types of heat capacity.
Heat capacity is given in kJ $\cdot$ K^-1
Specific heat capacity is given in kJ $\cdot$ g $\cdot$ $^{\circ}$ C^-1, because it is referring to the amount of heat required to raise the temperature of 1 gram of the substance by 1 $^{\circ}$ C^-1.

Diviya Khullar 1G

You don't include reactants that are acting as solvents. You also don't include zero order reactants but this is because they have an exponent of zero.

Diviya Khullar 1G

The stoichiometric coefficients correspond to the number of bonds present and when you are using bond enthalpies to calculate enthalpy you need to know how many bonds and broken or formed. So, to calculate this you need to multiply the number of bonds present in one molecule by the stoichiometric co...

Diviya Khullar 1G

You have to use mols in order to make sure the units cancel out with those of the gas constant.

Diviya Khullar 1G

You need to put a solid electrode, like Pt_(s), when there are no conducting metals already present to transfer electrons.

Diviya Khullar 1G

How do you find the rate constant for the following first-order reaction;
$2A\rightarrow B+C$ , given $[A]_{0}=0.153$ mol $\cdot$ L^-1 and that after 115s the concentration of B rises to 0.034 mol $\cdot$ L^-1.

Diviya Khullar 1G

What is the unit for the rate constant for a zeroth-order reaction?

Diviya Khullar 1G

You use the Nerst equation to find cell potential ( E_{cell} ) using the standard cell potential ( E ), gas constant ( R ), moles of electrons transferred ( n ), Faraday's constant ( F ), and the reaction quotient ( Q ). You just have to really read the question to determine what information you are...

Diviya Khullar 1G

When calculating the rate of a reaction, will the units include time? For example, will it be L $L\cdot mol^{-1}\cdot s^{-1} or L\cdot mol^{-1}$

Diviya Khullar 1G

Hi,
I am having trouble understanding conceptually what the order of a reaction is. What is the difference between a first and second order reaction?

Diviya Khullar 1G

How can we tell from a chemical equation such as $Ce^{4+}(aq)+I^{-}\rightarrow I_{2}(s)+Ce^{3+}(aq)$ whether or not we need to put an electrode such a Pt(s) in the cell diagram?

Diviya Khullar 1G

Also remember that if you are calculating Gibbs Free Energy using a formula that has a gas constant to consider the of R, for example, R=8.314 $J\cdot K^{-1}\cdot mol^{-1}$

Diviya Khullar 1G

In the 7th edition, it is everything before 4J.

Diviya Khullar 1G

Why does change in entropy decrease when temperature increases? I know it is because in the equation $\Delta S=\frac{q_{rev}}{T}$
temperature is on the bottom but what is the conceptual reason behind this?

Diviya Khullar 1G

P $\Delta$ V= $\Delta$ nRT is used when you are dealing with equations where the volume and the number of moles is changing.

Diviya Khullar 1G

\Delta U represents the change in internal energy. A positive \Delta U tells us that the internal energy of gas has increased (usually because the temperature increased and the molecules are moving faster.) A negative \Delta U tells us that the internal energy of gas has increased (because the temp...

Diviya Khullar 1G

Yes -P(V₂-V₁ is what you get when you solve $-P\int_{V1}^{V2}dv$

Diviya Khullar 1G

A closed system is able to exchange energy but not matter with its surroundings.
But an isolated system can exchange neither with its surroundings. For example, hot liquid in an insulated container.

Diviya Khullar 1G

An isolated and a closed system are two different types of systems. A closed system can exchange energy, but not matter with its surroundings. An isolated system can't exchange matter or energy with its surroundings.

Diviya Khullar 1G

I believe you are asking about the heating curve for water that was presented in class. It illustrates that during a phase transition, there will be heat going into the reaction but there'll be no change in the temperature of the sample because all of that work is being used for the phase change.

Diviya Khullar 1G

Another way you can check is by drawing a Lewis structure and checking to see if it has a lone pair to which an H⁺ can bond or to see if it has any hydrogen atoms that the compound can easily release.

Diviya Khullar 1G

You should not round off until the end. Only account for significant figures when you are at your final answer.

Diviya Khullar 1G

Q is the reaction quotient and K is the equilibrium. Q basically tells us the ratio of the concentration or partial pressure of the products to that of the reactants when the reaction is not at equilibrium, while K tells the same thing when the reaction is at equilibrium. Comparing the two not only ...

Diviya Khullar 1G

In response to a change in pressure (due to decreased volume), a reaction will either shift to the right or the left to maintain equilibrium. A quick way to predict how a reaction will react is: if there are more moles on the right, the reaction will shift to the left and if there are more moles on ...

Diviya Khullar 1G

K is the equilibrium constant and is used when the reaction is in equilibrium. Q is the reaction quotient and is what we need to find when the reaction is not in equilibrium or if we are not sure if the reaction is in equilibrium.

Diviya Khullar 1G

Regarding which K value to use because this question id dealing with concentration and is asking for [H₂], you will need to use K_c.

Diviya Khullar 1G

A dipole moment is created when there is an unequal sharing of electrons between two atoms. You will typically see this when a difference in electronegativity between the two atoms bonded together (for example O and H). The polarity of a molecule depends on whether the dipole moments cancel out or n...

Diviya Khullar 1G

The past exams have asked for the molecular geometry. I believe if you were being asked for the VSEPR geometry it would specifically say VSEPR.

Diviya Khullar 1G

You would have to add "ion" to the end of the name of a coordination complex with a positive or negative charge but not a coordination compound. The difference between these two is that a coordination complex stands alone with nothing outside of the brackets to counter the positive or nega...

Diviya Khullar 1G

Compounds with carboxyl group are usually acids. The H on the carboxyl group is the proton that the compound gives off in a reaction.

Diviya Khullar 1G

The Bronsted definitions of acids and bases relate to the protons. So a Bronsted acid is a proton donor and a Bronsted base is a proton acceptor. The Lewis definitions of acids and bases relate to the electrons. A Lewis acid is an electron acceptor and a Lewis base is an electron donor.

Diviya Khullar 1G

Ozone (O 3 ) is a polar molecule because when you draw the Lewis structure of the molecule you will see that it has a central oxygen with a lone pair of electrons, one oxygen double bonded to the central oxygen, and one oxygen single bonded to the central oxygen. This lone pair of electrons results ...

Diviya Khullar 1G

When a molecule is able to form H-bonds with molecules around it, it typically means it is polar. The only way molecules are able to form H-bonds is when the hydrogen atoms have a slightly positive charge, which is the result of unequal sharing of electrons.

Diviya Khullar 1G

Atoms that are covalently bonded usually have an electronegativity difference that is smaller and atoms that have an ionic bond have an electronegativity difference greater than 2.

Diviya Khullar 1G

I believe you simply have to memorize which acids and bases are strong and weak.

Diviya Khullar 1G

You can determine if a molecule is polar or non-polar by looking at its symmetry. If there are dipole moments that are across from each other and cancel each other out, the molecule is non-polar. Or, if there is equal sharing of electrons between the atoms of the molecule, the molecule is polar. If,...

Diviya Khullar 1G

Sigma bonds result from the head-on overlap of the orbitals of the two atoms, which has more area of overlap than pi bonds which result from the parallel overlap of orbitals. That is why sigma bonds are stronger.

Diviya Khullar 1G

Electrons aren't typically described as distorted, bonds are described a distorted when there is a lone pair of electrons in a molecule. Because of electron repulsion, lone pairs cause all other bonds to move away from them and closer to each other, resulting in distorted bond angles that are smalle...

Diviya Khullar 1G

I think we can draw the structure like that with the filled in and stripped wedge. But the more important thing is naming the correct molecular shape of the molecule.

Diviya Khullar 1G

I don't believe you will be expected to know specific bond lengths but you will need to know relative bond lengths. So you will need to know that single bonds are longer than double bonds and double bonds are longer than triple bonds. You will also need to know that atomic and ionic radii as well as...

Diviya Khullar 1G

I'm not sure I understand what you are asking. The VSPER shape of an electron can be tetrahedral when there is a central atom with four things bonded to it. The angles in a tetrahedral are 109.5 degrees because the four atoms bonded to the central atom want to be as far from each other due to repuls...

Diviya Khullar 1G

H, He, Li, and Be are exceptions to the octet rule because they are smaller atoms. In additions elements in Group 13 don't necessarily need to have a full octet.

Diviya Khullar 1G

When we are drawing a Lewis structure for a molecule, we want the formal charges of each atom to equal 0 or to equal the overall charge of the molecule. Often times determining which atom will carry a positive or negative formal charge depends on how electronegative the element is. For example, oxyg...

Diviya Khullar 1G

Group 13 elements don't need to fulfill the octet rule but they can fulfill the octet rule.

Diviya Khullar 1G

Elements want to achieve an electron configuration that is like the closest inert gas, because this is the most stable form for the atom to be in. So, they will lose or gain just enough electrons so that they can have a full outer shell or electrons. In the case of copper, it has 2 valence electrons...

Diviya Khullar 1G

An ionic bond usually occurs between a metal and a nonmetal, where the metal loses an electron to the nonmetal so that both atoms can be stable.
A covalent bond usually occurs between two nonmetals, where the two atoms share an electron so they can both be stable.

Diviya Khullar 1G

Elements in the s-block are more reactive. Yes, because they do have lower ionization energies, it is easier to remove electrons from the outer shell of these elements, making them more reactive. s-block elements usually have one or two electrons in the outer most shell, and it requires less energy ...

Diviya Khullar 1G

To figure this out you want to find the first three quantum numbers, which specify the orbitals of each electron. Your principal quantum number is n =2. Using this information, you can now figure out your other quantum numbers. First you want to find l . l can be any number from 0 to ( n -1). In our...

Diviya Khullar 1G

Higher orbitals have more energy because the electrons have higher potential energy. If an electron is able to gain more energy it can jump to a high orbital making it easier for it to be removed from an atom. So, because the electrons in higher orbitals have higher potential energy, the orbital is ...

Diviya Khullar 1G

The quantum number for the spin of an electron will be either +1/2 or -1/2 but I don't think we will be learning how to determine the spin of a specific electron in this class.

Diviya Khullar 1G

Something that is very small, such as an electron, has a wavelength that is large enough to be detectable.

Diviya Khullar 1G

The negative sign is there because a bound electron has lower energy than a free electron. So, it is there to represent the negative change in energy.

Diviya Khullar 1G

In order for something to be considered to have wavelength properties it has to have a wavelength that is larger than n x 10^(-18) m. Anything smaller than that is not easily detectable. So, in the example you are referring to the wavelength of the car was determined to be 1.64 x 10^(-38), which is ...

Diviya Khullar 1G

In this calculation you are typically multiplying or dividing, and the rule when it comes to significant figures in multiplication or division the rule is that your answer should have the same number of significant figures as the factor with the least number of significant figures. And also make sur...

Diviya Khullar 1G

Once you divide the each of the number of moles of each type of atom by the smallest value you usually get a whole number right away. But I was wondering what to do if you get a number that is slightly off, for example if you get 4.03 is it okay to use 4 for the number of atoms in the empirical form...

Diviya Khullar 1G

For the time being, I would just look up the state of the atom. Professor Lavelle said the more you do these problems throughout the course of the class you will be able to remember the states of many of the molecules.

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